Inflatable ball with composition cover and synthetic thread winding



1 'Sept. 4. 1956 c J CROWLEY ET AL 7 2,761,684

INFLATABLE BALL WITH COMPOSITION COVER AND SYNTHETIC THREAD WINDINGFiled Feb. 9, 1951 2 Sheets-Sheet l ATTORNEYD Sept- 4. 1956 c. J.CROWLEY ET AL 2,761,684

INFLATABLE BALL WITH COMPOSITION COVER AND SYNTHETIC THREAD WINDINGFiled Feb. 9, 1951 2 Sheets-Sheet 2 INVENTORS ATTO RN EYS United StatesPa en ,0

INFLATABLE BALL WITH COL [POSITION COVER AND SYNTHETIC WINDING vApplication February 9, 1951, Serial No. 210,174 A 3 Claims. (Cl.273-65) This invention relates to inflatable athletic balls, and hasparticular reference to spherical balls such as basketballs, soccerballs and volleyballs, although the invention is lot limitedvin allaspects to a spherical ball.

, An important object of the invention is to provide an inflatableathletic ball in which the size and shape of the article as manufacturedor fabricated will be maintained thereafter under effective control, andwill be kept within very close limits. H

A further object of-the invention is to provide a ball of. thebasketball type having a very strong wallstructure which is very simpleand easily built, and in which the use of rubberized fabric isalthogether eliminated or reduced to a minimum, and in which the processof manufacture is considerably simplified.

Another object is to provide a very durable ball which is playable andhasa resilient and, flexible coveror outer layer that is not subject tocrackingand breaking, and has further advantages as hereinaftersetforth.

Another purpose of the invention is to coordinate in an improved mannerthe several layers of material that are .used in theball wall, so that,with regard to. the finished ball as a unit, a considerableimprovementisprovided. a g n In the accompanying drawings: p a

Fig. l is an elevation of a basketball embodying the invention; a

- Fig. 2 is a broken view showing different layers of material in thewall; a a

1 Fig. 3 is an elevation showing the bladder after it has been coveredwith a winding of cord or thread;

Fig. 4 is a somewhat diagrammatic sectional view showing amanufacturingstep following the application of the cord winding I H Figs. 5 and 6 areviews similar to Fig. 4, showing later stages in the manufacture;

Fig.7 is a perspective view showing a formof cord usedin winding the"bladder; and

Fig. 8 is a perspective view showing a cord of modifiedform. I I By wayof example there is described a basketballand "the steps employed initsmanufac'ture. In making the ball shown, a spherical pre-curedvalve-equipped bladder of rubber is provided, and, after inflation ofthe bladder to such an extent that a rather firm's'phere of thepropersize isprovided, a winding of cord or thread is, applied to thebladder,the turns of the cord or threa'd being,

disposed approximately on great circles. Then, with or withoutpreliminary impregnation of the cord with rubberytackymaterial, a layerof uncuredrubber, called fintermediate rubber is applied to the winding.Then 'an uncured layer of cover stock is applied to the intermediaterubber, the same being a curable material such 'as hereinafterdescribed. Following this, the article is placed in a mold and inflatedso as .toshape properly and densify the wall structure; as hereinaftermore particularly described.

- i In the gs; the rubber bladder is indicated at 10:

3 2,761,684 C Patented sep 4 .5

and the inflating valve at 11. The valve may advan tageously be. of thetype shown in the Delaney and Madsen Patent No. 2,065,121, datedDecember22, 1Q36'. The valve has a rubber stem 11' into which theinflating needle can be introduced, and whichv extends through the ballwall so as to be accessible atthe exterior. Thecord with which thebladder is wound is shown at 12, the in termediate layer at 13, and theouter layer, which provides the cover, at 14. The structure of theballw'ill be more fully understood from the following description of apreferred method of constructing the ball. 7

The bladder 10 has a relativelythin rubber wall, and it may be made byaccurately cutting a number of quadrants and seaming them together inthe manner described in the Madsen Patent No. 2,218,919, of October,22', 1940, and then molding the bladder accurately to shape in aspherical mold. By proceeding in this manner it is possible to provide aprecisely spherical bladder. The bladder is vulcanized in the process ofmaking it, as by heating of 'themold, so that the spherical shape willbe maintained. In the process of making the ball the bladder is inflatedto provide a rather firm sphere of the proper size. The next step is toapply the winding of cord, this winding being applied directly to thebladder surface over the entire surface except for the inflating valvestem. One end of the cord 12 is adhered to the bladder surface in asuitable manner, as by using a little piece of uncured rubber foradhesion purposes, and the winding is then commenced and carried on insuch a manner that a relatively thin and open layer of intersecting cordturns is provided, the turns being disposed substantially on greatcircles.

Before the layer of intermediate rubber 13 is applied to thecordwinding, the cord may be impregnated with a suitable curableimpregnating substance in liquid form which is rubbery and tacky. It ispreferred to impregnate the cord with such a tackifying agent, but it isnot necessary in all cases.

The next step is to apply the intermediate rubber, and this is donepreferablyby' applying to the wound bladder athin cover of uncuredrubber sheet, the cover being made up of quadrants which are joinedtogether at their adjacent edges so as to provide a complete coveringlayer through which the valve stem projects.

Thenext step is to applythe external layer or cover 14. For this layer aspecial rubber compound is used, as hereinafter described. This compoundin uncured condition, and in the form of a sheet, is applied to thearticle in substantially the same. manner as the intermediate rubberlayer is applied.

; .The nextstep is toplace the article or blank, made up as previouslydescribed, in a mold having. aspherical inner surface,- in which moldthe ball wall will be condensed under air pressure and given its finalform. The mold is usually heated so that, concurrently with the shaping,the curable components in the wall structure will. be curedorvulcanized. The inflation of the ball in the process of molding iscarried out by introducing air into the bladder through the inflatingvalve.

After the steps justdescribed, the articlehaving been leftin the moldfor aperiod sufficient for'complete setting and curing, the ball isremoved from the mold, and afterminor finishing operationsis readyforuse. jd d In the drawings the showing of the'cor'd layeris somewhatdiagrammatic, and in practice the number of turns of cord will usuallybe in excess of those shown in Fig. 3, although the'layer of cord willbe relatively thinand relatively open. The openings or interstices. thatL go through the winding layer may have an areafwhich averages fsay,.005 sq. in. This figure is also given only byway of example- Where thecord is madeof synthetic fiber,' sucha's nylon, it has greatstrength,'and a thin has the additional advantage of firmly anchoringand holding the intermediate rubber on account of the fact that theintermediate rubber goes through the interstices of the winding and hasthe cord turns well distributed through the thickness of theintermediate rubber layer, as shown in Fig. 6.

It is preferred to use for the cord material 12 a special. cord formedof nylon, a portion of such cord, greatly enlarged, being illustrated inFig, 7. In this form the cord 12 comprises two intertwisted fibrousstrands or elements of nylon, one of which, indicated at 12', is ofrelatively large cross section, and the other of which, indicated at12", is of relatively small cross section. The thicker element 12' iscomposed of continuous parallel filaments, and the thinner element iscomposed of short or staple fibers spun together in a body to create ayarn-like member from which the fine short fibers project, as shownsomewhat schematically in Fig. 7. The short fibers may have a length ofsay one inch to three inches, and this provides upon the yarn a largenumber of fine filamentary projections. The two elements or strands areintertwisted in the manner schematically shown in Fig. 7, the element12", on account of its smaller diameter, taking more of the twist ordeviation. One effect of combining the two elements in this manner is toprovide a cord of two strands or components, of which the larger isrelied upon for providing strength in a linear direction, while theother component, by virtue of its being twisted about the first one,provides a ridge formation, or, in other words, rib-like rougheningmembers or portions upon the cord, as well as providing the projectingorexposed ends of the fine short fibers.

A cord structure as above described is of particular advantage where, asin this case, the cord turns are substantially on great circles andintersect each other, because the cord turns are securely held in placerelatively to each other and to the inflated bladder by reason of theinterengagement of the roughening or ridge formation of crossing turns,and also the interentanglement of the fiber ends of one turn with thoseof an intersecting and contacting turn. It will be apparent'how a cordportion such as shown in Fig. 7 will interlock and become entangled witha similar cord portioncrossing and contacting the first portion. It willalso be apparent that a cord of this kind provides most effectiveengagement and embedment of the intermediate rubber when, in the courseof making the ball, the intermediate rubber and the cord layer areforced toward each other under the molding pressure. I V

The bladder, being pre-cured, gives greater resistance to the threadsthan does the intermediate rubber. j The thread turns, while becomingembedded in the intermediate rubber, usually do not to any great degreego beyond the outer surface of the intermediate rubber layer althoughthey do roughen this surface to a certain extent by providing thereon a,multiplicity of ridge-like formations. These ridge-like formationsnaturally are of considerable value because they press to acertain"extent into the inner surface of the covering layer'so as to interlocktherewith. The roughening and interlocking effect upon the coveringlayer and upon the bladder is indicated in'Fig. '6, which shows on anenlarged scale a portion of the wall of the completed ball.

' In Fig. 8 there is shown at 15 a plain cord which can, if desired, beused in place of the special cord shown in Fig. 7. The cord 15 is madeof synthetic fibers, preferably nylon fibers, and in the particular formshown is one made up of a large number of parallel continuous filaments.Such a cord has great strength and this makes it possible to provide awinding layer which is relatively thin and open, as above described,although the features provided by the ridge formation of'spun fibers areabsent. In some cases a cotton cord'can. be used.

The rubber used in the intermediate layer--13 is cus- 4 tomarily anordinary rubber compound comprising natural rubber or synthetic rubber.The covering layer, however, is of a special composition employing, inconjunction with natural rubber, a certain amount of high styrenestyrene-butadiene copolymer, the composition being of such characterthat the cover is markedly superior to a rubber cover or a cover ofleather. In the cover we use there may be employed, with natural rubber,a copolymer having 75% of styrene and 25% of butadiene. With these tworubbers there are used inorganic activators, a certain amount ofsulphur, and a suitable accelerator, the ingredients being mixedtogether by customary mixing procedures and the compound being veryreadily cured by bringing it to a vulcanizing temperature.

The composition used for the cover stock is especially valuable inproviding material that is more resilient than compositions previouslyused for the same purpose, thereby making the ball more playable. Theball is also made more durable by reason of the fact that the coverlayer flexes with the underlying part of the ball and does not breakaway on continued flexing, as has commonly been the case in the past.When the covering layer is too stiff it is very likely to be broken orruptured as the underlying carcass of the ball is'repeatedly flexed, butin the present case the covering layer, being very flexible, readilyfollows the flexing of the carcass.

In balls such as basketballs and footballs it is common practice toprovide in the outer ball surface a number of grooves such as shown inFig. 1, which are formed in the material of the covering layer for thepurpose of providing a better grip upon the ball, and in these groovedportions or parts of such portions the covering layer is customarilythinner than in other regions and more susceptible to cracking onflexing of the carcass. The flexibility of the covering layer providedupon the present ball is sufficient to overcome or inhibit the crackingof the cover within the grooves, and the longevity of the cover isincreased inasmuch as the flex life is exceptionally long. Anotherfeature of great advantage also is the strong adhesiveness of the coverlayer to the layer of intermediate rubber.

The following is a typical cover stock composition, the ingredientsbeing measured by weight:

Example No. 1

' Percent Natural rubber 52.0 75/25 styrene-butadiene copolymer 28.0Inorganic activators 12.5 Coloring pigment 2.0 Organic accelerator 3.0Sulphur 2.5

Another example of the cover composition is as follows:

Example N0. 2

As far as the styrene-butadiene copolymer is concerned, the percentageof styrene may vary between and 60. Above the upper limit the copolymerbecomes too stiff, and below the lower limit the composition will lack,among other qualities, the necessary strength and durability, and alsothe leathery feel which is characteristic of the composition will not bepresent.

For the cover composition the ranges ofthe natural rubber,styrene-butadiene copolymer and inorganic activators are:

Natural rubber from 45% to 55% High-styrene styrene-butadiene copolymerfrom 35% to 25% Inorganic activators from to As is apparent, thecomposition includes in addition coloring matter, sulphur, and anaccelerator. These may be varied in amounts so as to accord with thecharacteristics of the principal ingredients above named, and to meet asfar as possible the existing conditions and requirements.

Tests of compositions made up as herein described reveal that theinitial tensile strength is in the range of 2500 lbs. to 2750 lbs., theelongation in the range 425% to 450%, and the tear resistance, asmeasured by the A. S. T. M. rubber tear test, in the range of 90 lbs. to110 lbs. per square inch. In connection with the tear resistance, it isnoted that in comparison to previous compositions used for the purposethe tear resistance figure is rather low, but it is quite sulncient forthe purposes in view by reason of the fact that the cover layer is soflexible and flexes so easily with the underlying layer of fibrousmaterial made up of fabric, cord or the like. With regard to resistanceto abrasion, this, of course, is of great importance, especially asbasketballs and like balls are commonly used on outdoor courts ofconcrete or trap rock as well as on polished gymnasium floors.Compositions of this kind meet all of the requirements in this respect,as it has been found that these compositions, as tested by the Tauberabrasion test, show a loss of the order of 1.5% in weight in 2,000revolutions of the emery wheel.

It has also been determined that these compositions pass the customaryaging tests and have the necessary longevity. The cover stock has beentested likewise for resiliency, and admirably meets the requirements inthis respect, the resiliency being quite high considering the greatabrasion resistance of the cover. The flexibility of the covering layeris also high so as to present the advantageous features mentioned above.The resiliency and flexibility of the cover stock will, however, benoticeably less than that of the intermediate rubber providing the layer13. The rubber in layer 13 is preferably quite soft, bouncy andresilient, for the purpose of providing a cushioning layer between thecover and the bladder. Were it not for this relatively soft intermediatelayer the ball in playing condition would be too stiff and hard andwould not have the desirable playing qualities that are provided in thisinstance. The ball wall has ample resiliency and bounce where thecovering layer is backed up by the cushioning layer, without, on theother hand, using a greater internal pressure than, say, 8 or 9 pounds,and by being able to use a relatively low air pressure in the ball so asnot to make it too hard the stinging of the hands of the players or likedetrimental effect is avoided.

For the bladder it is preferred to use butyl rubber, because this holdsair better than other rubbers. It is not necessary to use butyl rubber,however, in all cases. Where butyl rubber is used there is a certaindecrease of resiliency in comparison to natural rubber, but in our ballstructure this low resiliency is compensated by the resiliency given tothe intermediate cushioning layer which is greater than that of thebladder. It is, therefore, clear that the character of the cushioninglayer modifies the resiliency and other characteristics of the ball in amanner to compensate for characteristics possessed by the covering layerand the bladder, respectively.

It is usually preferred to make the bladder wall considcrably thinnerthan the other two layers, as shown in Fig. 6, but variation may be madein this and other respects.

For a basketball having an outside diameter of 9%; inches the wall mayhave, for example, a thickness of 6 .130 inch, of which the bladderthickness 'is .020, the in-' termediate rubber (and cord) thickness .070inch, and the cover .040 inch. These dimensions are by way of exampleand for purposes of explanation.

The cover stock as above described has good adhesion to the intermediaterubber, and, where the cord turns project outwardly from theintermediate rubber, to the cord turns of nylon. The intermediaterubber, onthe other hand, has very good adhesion to the cord turns andto the bladder. In addition to the good adhesion between the cover andthe intermediate rubber, and between the bladder and the intermediaterubber, so far as adhesion per se is concerned, there is the lockingelfect heretofore mentioned produced by the cord turns that are embeddedin the intermediate layer and provide on said layer ridges orprojections that extend into and interlock with the adjacent layers. Theeffect just referred to, moreover, is increased owing to the fact thatthe cord layer is a relatively thin one presenting relatively largeinterstices in which the intermediate rubber is engaged and locked.

It will be seen from the foregoing that it is made possible to provide aball that is shaped very precisely and has a tough durable wall thatwill maintain its shape in hard service. The process of making the ballis very simple and the amount of textile fiber used in the ball isreduced to a minimum. While having the necessary strength anddurability, the ball wall can be made relatively thin in comparison toprior balls of this general type. So far as the ofiicial specificationsof the ball are concerned, such as size, weight, etc., these can be metwith relative ease. Owing to the fact that only a relatively smallamount of fibrous material is used in the ball wall, the proportion ofthe wall thickness given over to the abrasive-resistant cover stock canbe increased in comparison to prior ball structures, thus giving theball a longer life.

A further important advantage of the new ball is that, with a cover ofthe described composition, there is elimination of undesirable noise orso-called squealing effect incident to squeezing or high compression ofthe ball in play.

The term rubber is used herein in a broad and general sense unless thereis indication to the contrary.

Various changes can be made in the ball structure as herein describedwithout departure from the principles of the invention or the scope ofthe claims.

What we claim is:

1. An inflatable athletic ball having a valve-equipped bladder of butylrubber, a relatively thin and open winding of cord comprising syntheticfibers having the cord turns substantially on great circles and in closeproximity to the outer surface ofthe bladder, the cord comprising aninner element of continuous filaments having a surface roughening ofridge-like formation acting to anchor the cord turns relatively to eachother and to the bladder, a cushioning layer of rubber embedding saidcord turns and extending through the interstices between them, therubber of said cushioning layer being more resilient than that of saidbladder, and an outer cover applied to said cushioning layer comprisingnatural rubber mixed with a lesser amount of styrene-butadiene copolymercontaining between 60% and of styrene.

2. An inflatable athletic ball of spherical shape having an inflatablevalve-equipped bladder, a layer made up of turns of cord or threaddisposed on great circles having the innermost turns lying against theouter surface of the bladder in the entire external area of the bladderexcept for the valve area, the winding being relatively thin and havingrelatively large interstices and the cord or thread being of syntheticfibers and formed of two strands twisted together, one of these strandsbeing a heavier strand composed of parallel filaments and the otherstrand being a lighter strand of a yarn-like character having externallyprojecting filaments, said projecting filaments serving to anchor thecord turns of the open winding to each other and to the bladder, acushioning layer of soft bouncy rubber embedding the cord turns andextending through the interstices between them and into bondingrelationship to portions of the bladder, and an outer cover applieddirectly over and bonded to said cushioning layer comprising naturalrubber and a lesser amount of a styrene-butadiene copolyrner having astyrene content between 60% and 80%, the cushioning layer and the cordturns constituting the entire filling between the bladder and the cover.7

3. An inflatable athletic ball having a valve-equipped spherical bladderof butyl rubber, a relatively thin and open winding of cord comprisingsynthetic fibers laid directly against the bladder surface substantiallythroughout its area and having the cord turns substantially on greatcircles, the cord having an inner element of continuous filaments and anouter element of less diameter twisted about the inner elementcomprising spun fibers having projecting filamentary ends for anchoringpurposes, a cushioninglayer of rubber embedding said cord turns andextending into contact with the bladder surface, and

References Cited in the file of this patent UNITED STATES PATENTS2,053,123 Alles Sept. 1, 1936 2,273,200 Hoif Feb. 17, 1942 2,300,441Voit et al. Nov. 3, 1942 2,399,324 Clark Apr. 30, 1946 2,477,652 RobbinsAug. 2, 1949 OTHER REFERENCES industrial and Engineering Chemistry, vol.38, No. 9, published September 1946, pp. 955-958 cited.

Modern Plastics, July 1948; pp. 9396.

Modern Plastics, February 1950; pp. 72-74.

1. AN INFLATABLE ATHLETIC BALL HAVING A VALVE-EQUIPPED BLADDER OF BUTYLRUBBER, A RELATIVELY THIN AND OPEN WINDING OF CORD COMPRISING SYNTHETICFIBERS HAVING THE CORD TURNS OUTER SURFACE OF THE BLADDER, THE CORDCOMPRISING AN INNER ELEMENT OF CONTINUOUS FILAMENTS HAVING A SURFACEROUGHENING OF RIDGE-LIKE FORMATION ACTING TO ANCHOR THE CORD TURNSRELATIVELY TO EACH OTHER AND TO THE BLADDER, A CUSHIONING LAYER OFRUBBER EMBEDDING SAID CORD TURNS AND EXTENDING THROUGH THE INTERSTICESBETWEEN THEM, THE RUBBER OF SAID CUSHIONING LAYER BEING MORE RESILIENTTHAN THAT OF SAID BLADDER, AND AN OUTER COVER APPLIED TO SAID CUSHIONINGLAYER COMPRISING NATURAL RUBBER MIXED WITH A LESSER AMOUNT OFSTYRENE-BUTADIENE COPOLYMER CONTAINING BETWEEN 60% AND 80% OF STYRENE.